MPS II – Hunter Disease

Hunter Disease

Bronwyn Conneely

Hunter disease is one of the mucopolysaccharide diseases and is also known as MPS Type II. Hunter disease takes its name from Charles Hunter, the professor of Medicine in Manitoba, Canada, who first described two brothers with the disorder in 1917.

What causes this disease?

Mucopolysaccharides are long chains of sugar molecules used in the building of connective tissues in the body. ‘Saccharide’ is a general term for a sugar molecule (think of saccharin), ‘poly’ means many and ‘muco’ refers to the thick jelly-like consistency of the molecules.

There is a continuous process in the body of replacing used materials and breaking them down for disposal. Children with MPS II are missing an enzyme called iduronate sulphate sulphatase which is essential in cutting up the mucopolysaccharides called dermatan and heparan sulphate. The incompletely broken down mucopolysaccharides remain stored in cells in the body causing progressive damage. Babies may show little sign of the disease but, as more and more cells become damaged, symptoms start to appear.

How is this disease inherited ?

Hunter disease has a different form of inheritance from all the other MPS diseases as it is ‘sex linked’ like haemophilia. Girls may be carriers of the disease but, except in very rare cases, only boys will be sufferers. The few girls who have been found to have the disease have an associated chromosomal abnormality.

All families of children with Hunter disease should seek further information from their doctor or from a genetic counsellor before planning to have more children. If the mother is a carrier there is a 1 in 2 risk that any boy born to her will have the disease and that any girl will be a carrier.

The sisters and maternal aunts of an individual with MPS II may be carriers of the disease who would also have a 1 in 2 chance of passing the disease to a son.

In many families it is possible to detect female carriers by direct analysis of the genetic material. The doctor may wish to take a sample of blood from your affected child so that the exact genetic abnormality can be detected.